By http://sagnanet.is/saganet/?MIval=/SinglePage&Manuscript=707&Page=332&language=english%20JS%20392%208vo / Transferred from en.wikipedia to Commons., Public Domain, https://commons.wikimedia.org/w/index.php?curid=6763063

Image Credit:

By http://www.robgendlerastropics.com/NGC6946-Subaru-Gendler.html
Luminance data from the Subaru Telescope (NAOJ) and Hubble Space Telescope, RGB data by Robert Gendler